This application claims priority of United Kingdom patent Application No. 0010282.2, filed on Apr. 27, 2000.
The present invention is concerned with electrical connectors, and particularly (but not exclusively) with compliant electrical connectors for use in planar array filters.
A particularly important application of the present invention relates to filtration of electromagnetic interference (EMI). It is increasingly important to filter EMI from electronic signal interconnections because this spurious interference can otherwise cause serious malfunction of electronic systems.
Conventionally this is achieved in a volumetrically efficient way by incorporating a ceramic planar array inside a multi-way connector. A typical example of this is shown in UK Patent No. 2205201.
Ceramic planar arrays are multi-layer structures whereby metal electrodes 40 are interleaved with ceramic dielectric layers in a monolithic block 50 with lead through holes 4 corresponding to the multi-way contacts of the connector. The electrodes serve as capacitor plates and are designed so that each lead through has a separate capacitance to earth. That is, each lead through is connected to one side of a capacitor the other side of which is connected to the connector outer metal shell which contacts each through a chassis.
The lead through holes in the planar array are metallised, the metallisation being connected to selected electrodes (ie. to one side of the multi-layer capacitor which is to be electrically connected to the lead through contact). The signal is carried by lead through contacts in the form of elongate pins. Clearly there is a requirement for a connection to be formed between the metallisation and the lead through contact itself. This has traditionally been achieved by using a solder connection (eg. as described in GB2214513A) or a spring clip.
An object of the present invention is to provide for the required connection in a robust, reliable and constructionally straightforward manner.
In accordance with a first aspect of the present invention there is an electrical connector comprising an at least substantially helical winding shaped to provide a first portion, having a diameter suitable to receive and embrace an electrical contact inserted therein, and a second portion of larger diameter than the first for contacting an electrical terminal disposed around or adjacent the contact, to thereby form an electrical connection from the contact to the terminal.
The winding may be formed of metal, whose compliance assists in assuring reliable electrical contact.
Benefits which accrue from this simple arrangement include much reduced assembly costs and stress free, compliant, reliable electrical contact, there being no soldering heat nor direct rigid mechanical connection.
The stress produced by temperature changes is also much reduced by having a compliant contact so that expansion/contraction of the metal parts of the connector do not bear upon the brittle ceramic of a planar array.
A planar array utilising connectors according to the present invention can in addition be designed to be repairable, noting that the earth connection to the array is usually sprung from the outer connection of the planar array to the inside of the connector shell.
By making the internal diameter of the first portion smaller than the external diameter of the contact to be inserted therein it can be ensured that pressure and electrical contact between the two is maintained.
The external diameter of the second portion may be selected to be larger than the internal diameter of an electrical terminal formed as a bore into which the second portion is insertable, so that the second portion is radially, compliantly compressed within the bore to maintain pressure and electrical contact between the bore""s inner surface and the second portion.
The connector may be formed to function as a compression spring when retained between two opposed, axially facing surfaces in order that the connector may form an electrical connection to at least one of the surfaces.
In certain arrangements the connector may be both radially and axially compliantly deformed.
According to a second aspect of the present invention there is an electrical connection arrangement comprising a connector constructed according to the first aspect of the present invention.
According to a third aspect of the present invention there is an electronic filter comprising a block containing electrodes forming at least one capacitor, at least one lead through hole in the block receiving a lead through contact, and a connector according to the first aspect of the present invention forming an electrical connection from the lead through contact, which is received in the connector, to metallisation of the lead through hole and so to one or more of the electrodes.